1. Field of the Invention
The field of the invention is primarily that of means for generating electrical current. More particularly, the invention is concerned with a form of thermopile, that is a plurality of series connected thermocouples.
Though thermopiles have a wide utility, the improved construction of this invention is particularly adapted for use as a generator for generating multiple EMF outputs in response to the presence or absence of heat from a pilot flame in gas fired or other installations. Moreover, the increased sensitivity of this thermopile allows for a faster response to activate or deactivate a valve or other device connected to it.
2. Description of Related Art
The relevant prior art is found primarily in the field of pilot generators utilized in gas-fired heating systems. A form of pilot generator embodying a thermopile has been in use for many years. This particular form consists of first and second groups of dissimilar metals arrayed in a circle and positioned against the inner side walls of a metal tube or sleeve. In a common form of the device, the elements were in the form of flat metal bands with hot and cold junctions being provided by way of welds at the ends between the flat end surfaces of the bands, the hot junctions being at one end and the cold junctions at the other. Typical dimensions of this type of construction are known in the art. In the known commercial constructions, typically there have been 12 or more thermocouples. The prior art constructions described above were subject to some drawbacks. The reduced efficiency of the prior art construction due to the mass of the sleeve and placement of the thermocouples relative to the sleeve decreased the ability of the thermopile to respond fast enough when in the presence and absence of a flame. The slower response time slowed the opening of a valve and created a potential hazard in the delayed closure of the valve in the event the pilot flame was extinguished. In addition, the device typically provided only one EMF output operating only one safety device.
An array of thermopile elements of dissimilar metals with one longer pair of elements of dissimilar metals is arrayed in a circular pattern within a metal sleeve or jacket to which heat from a pilot flame is applied. The thermopile elements are elongated elements, the dissimilar metals preferably being nickel chrome alloy and nickel copper alloy or iron alloy and iron constantan, the hot junctions being at one end of tile tubular array and the cold junctions at the opposite end. In the preferred embodiment, there may be 12 or more junctions. A cluster of long elements composed of two dissimilar metals are assembled with one end of one element joined with one end of a second element to form hot and cold thermocouple junctions that are arrayed in a circle. One of the groups of two dissimilar metals, being longer than the rest of the array, extends beyond the other hot junctions, thereby allowing for that hot junction greater sensitivity and responsiveness to changes in the temperature of the pilot flame and surrounding radiating surfaces. Insulation is provided in accordance with teachings well known in the art.
The primary objective of this invention is to provide an improved thermopile construction particularly of the type wherein the thermopile elements are arrayed in a circle within a tube or sleeve.
A further object of this invention is to provide an improved thermopile formed of a plurality of elongated dissimilar elements and having one longer pair of dissimilar elements extending beyond the others allowing for greater sensitivity and a faster response time to changes in the temperature of a pilot flame and surrounding radiating surfaces.
Another object of this invention is to provide an improved thermopile that is capable of providing multiple EMF outputs to operate multiple electromechanical or electronic devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a typical pilot burner with associated pilot burner;
FIG. 2 is an exploded schematic view illustrating the thermopile elements of the herein invention;
FIG. 3 is an enlarged view of a section of the thermopile elements and the junctions;
FIG. 4 is an isometric view of a preferred form of the pilot generator;
FIG. 5 is a sectional view taken along the line 5xe2x80x945 of FIG. 4.